This is a rate of homogeneous nucleation estimated for a model of water, not real water in experiments we cannot grow nuclei of water and so cannot directly determine the values of the barrier " & Delta; G * ", or the dynamic parameters such as " j ", for real water.
32.
However, it may be that indeed the homogeneous nucleation of ice at temperatures near-20 & # 8239; �C and above is " extremely " slow and so that whenever we see water freezing temperatures of-20 & # 8239; �C and above this is due to heterogeneous nucleation, i . e ., the ice nucleates in contact with a surface.
